Multivibrator



Dc. 19, 1944. H, R K 2,365,512

MULTIVIBRATOR Filed March 24, 1943 Inventor: Evert-ward H.B.Bar-telink,

Mis t'horney Patented Dec. 19, 1944 MULTIVIBRATOR Everhard H. B. Bartelink, West Milton, N. Y., as- :signor to General'Electric Company, axcorporation of New York Application March24, 1943, Serial'No. 480,337

3 Claims. '01. 25 36) My invention relates to multivibrators and particularly .to synchronizing means therefor. My present application is a continuation in part of my application Serial No. 342,321, filed June 25, 1940, and which is assigned to the assignee of my present application.

My'present invention has for one of its objects to provide improved synchronizing means for such multivibrators.

Another object of my invention is to provide means to reduce certain undesired capacity effects in the operation of synchronizing means for multivibrators.

A further object of my invention is to provide means to neutralize the effect of such undesired capacity as may exist between the anode of one of the discharge devices of the multivibrator and the anode of a'device employed for synchronizing the multivibrator the anode of which'device varies in potential oppositely to that of the anode of said one device,

'The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken :in connection with theaccompanying drawing in which the single figure represents an embodiment of my'invention.

Referring to the drawing, I have indicated therein a pairof electron discharge devices I and Device I has an ano'de 3, a control electrode 4 and a cathode 5. Device 2 has an anode 6, a control electrode 1 and acathode '8. The anodes 3 and 6 are connected through individual resistances 9 and Ill and a common resistance ll to the positive terminal of a source of operating potential 12. The cathodes and 8 are connectedthrough individual resistances l3 and M to the negative terminal of the source of potential I2. is coupled to the anode of the opposite device through respective condensers I 5 and I6, and the two control electrodes are connected together through a series of resistors I1, l8 and I9, a variable tap on the intermediate resistor l8 being connected to ground with respect to alternating current by means of a large capacitor and it is connected for direct current through a resistance 2! to a variable tap 22 on a bleeder resistance 23 across the source of potential l2,

The circuit arrangement as thus described comprises the usual .multivibrator i which the two The control electrode of each device control electrodes are biased positively with respect to the cathodes of the two devices by a variable amount dependent upon the position of tap 22 onresistance 23.

When a pulse of current flows in either device, the anode potential on the respective device drops by reason of the potential in the respective resistance 9 or "Ill and this drop in potential is transmitted to the control electrode of the op- ;posite device through the respective capacitor IE or Hi, this potential being sufiicient to interrupt current in the opposite device. This interruption in currentcauses an increase in potential on the anode of the opposite device which in turn, be cause of the capacity between it and the control electrode of the first device, tends to vary the potential on the control electrode of the first device in the positive direction producing an accumulative action whereby one device becomes saturated and the other device becomes cutoff. After discharge of that one of the two condensers which maintains its respective control electrode negative to a point such'that current flows in the corresponding discharge device, the accumulative non-conducting becomes conductive and the other becomes non-conducting. 'In this way, the two devices become conducting cyclically and at a frequency which is-dependent upon the position of the tap '22. Thus'pulses of currentflow in theresistances 9, I0 and. in the -cathode resistances l3 and I4.

Resistance l4 may be included in the anodecathode circuit of a third electron discharge device comprising cathode 25, anode 2'! and control electrode 28, which device is likewise connected across the source of operating potential through the cathode resistance l4 and anode resistance 29. When a pulse of current flows in resistance 14, the current in the device 25, 21, 29 is reduced and thus a corresponding pulse in the positive direction appears between conductors 30 and 33 to which a suitable load may be c'onnected.

If desired, however, positive pulses may also be taken from conductors 30 and 34.

It is frequently desirable that the pulses produced by the multivibrator thus described be synchronized by a source of pulses represented by the circle 4|], which source is connected between the control electrode of discharge device 46 and the cathode thereof. The cathode of device 46 is connected to the cathode 5 and the anode is connected through a resistance 41 and resistance H to the source of anode operation potential. If

desired, the device 46 may be in the same envelope with the electrodes 3, 4 and 5, as illustrated. In operation pulses produced by source 48 are transmitted by device 46 and appear on resistance 13. These pulses vary the potential on cathode in a positive direction with respect t ground and thus tend to interrupt current between anode 3 and cathode 5. When this happens, the anode potential of device 3 rises thereby driving the control electrode 1 positive, which increases the current in device 2 thereby reducing the potential on the anode 6 which, through action of condenser 16, renders the control electrode 4 more negative with respect to the cathode thereby further reducing the current in device I. Through this action the multivibrator is synchronized with the pulses from th source 40.

It may happen, however, that undesired capacity exists between the anode 48 of device 46 and the anode 3. This capacity may exist by reason of the fact that these two anodes are enclosed in the same envelope or it may exist by reason of external circuit connections. Such capacity is indicated in dotted lines at 49. It will be seen that, owing to the coupling resistance l3 which couples the device 46 in the device .i, the potential on the anode of these two devices varies oppositely; that is, when current flows in device 46, its anode potential drops. The resulting potential on resistance l3, however, reduces the current in anode 3 causing that anode potential to rise. This is the desired action of the device. However, the drop in potential on anode 48 may be transmitted to the anode 3 through capacity 49 during the initial part of the pulse. This capacity may be sufiiciently great that the multivibrator is synchronized by the potential supplied to the anode device 3 through capacity 49 rather than by the potential on resistance l3. The effeet, in that case, is that the multivibrator produces a positive pulse when it is desired that it produce a negative pulse.

To avoid this eiTect and in accordance with my invention, the condenser 50 is included in the circuit between the anode 48 and the anode 6.

-When the potential of anode 3 varies in the positive direction, the potential of anode 5 varies in the negative direction. The potential variation on the anode 48 is supplied to both of the anodes 3 and 6, one of which varies in a positive direction and the other in a negative direction. Thus the effect of capacitance 49 is neutralized by the capacitance 50. In other words, when the potential of anode 48 drops due to current flowing therein, it tends to cause the potential on anode 3 to drop by action of capacitance 49. However, at the same time, the potential on anode 6 rises which in turn, through capacitances 50 and 49, tends to increase thepotential on anode 3, this tendency just neutralizing the tendency produced by the rise in potential on anode 48 due to capacitance 49 alone.

While I have shown a particular embodiment of my invention, it will, of course, be understood that I do not wish to be limited thereto since difierent modifications may be made both in the circuit arrangement and in the instrumentalities employed, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, a multivibrator comprising site variations, and means responsive to current in the second of said pair of devices to neutralize the effect of said undesired capacity.

2. In combination, a multivibrator comprising a pair of electron discharge devices connected in multivibrator relationship, a third electron discharge device having an anode having capacitive coupling to the anode of one of said pair of devices, means responsive to current in said third device to reduce current in said one device thereby to synchronize said multivibrator with current variations in said third device, and capacity coupling between the anode of said third device and. the anode of the second of said pair of devices proportioned to neutralize the eflect of said first capacity coupling on the anode of said one device.

3. In combination, a multivibrator comprising a pair of electron discharge devices connected in multivibrator relationship, and each having an anode and a cathode, a third electron discharge device having a cathode and anode, a source of operating potential having a positive terminal connected through individual resistances to all of said anodes and having a negative terminal connected to all of said cathodes,a common resistance in circuit between said negative terminal and the cathodes of said third device and one of said pair of devices and individual capacity coupling between the anode of said third device and the respective anodes of said pair of devices said coupling being proportioned to reduce the eifect on the anode of said one device of capacity between said anode and the anode of said third device, and a pulse source connected to said third device to synchronize said multivibrator.

EVERHARD H. B. BARTELINK. 

